Device for electrolytic surface treatment of bulk material

ABSTRACT

For electrodeposition of metal from an electrolyte with a vibrator conveyor the bulk material is transported in a conveying trough which is connected as cathode. According to the invention, the conveying trough (18) is provided with supporting stringpieces (22 to 29) which are intended for the mechanical attachment of the conveying trough (18) on the central pipe (2) as well as for current transmission to the cathode and furthermore serve as electric lead-through through the sidewall (5) of the central pipe (2). The supporting stringpieces (22 to 29) comprise an electrically conducting contact shaft (52) which is electrically insulated from the electrolyte (12) and the central pipe (2). For the attachment of the conveying trough (18) on the stringpieces (22 to 29) contact bolts (56 to 58) are provided which serve at the same time for current transmission from the contact shaft (52) to the bulk material (20). In this form realization one obtains a simple current supply to the cathode.

BACKGROUND OF THE INVENTION

The invention relates to a device for the electrolytic surface treatmentof bulk material, preferably for electrodeposition of metal from anelectrolyte, with a vibrator conveyor whose conveying trough isconnected to a central pipe. The conveying trough of the vibratorconveyor is arranged spirally around the central pipe and surrounded bya vessel which is provided with at least one feed and one dischargeshaft for the bulk material. This vessel contains the electrolyte, intowhich the vibrator conveyor with the central pipe dips partially.

Since in the surface coating of bulk material with aluminum the accessof air and atmospheric moisture to the electrolyte brings about aconsiderable reduction of the conductivity and useful life, theelectroplating must be carried out in an apparatus operating underexclusion of air. In order that access of air can be prevented alsoduring loading and unloading of this apparatus operating under exclusionof air, also feed and discharge locks are required, which may bedesigned as gas locks, as liquid locks, or as combined gas-liquid locks.

In a known device for mass electroplating of metal, a vibrator conveyorwith a horizontal and a vertical oscillation component is provided forthe transport of the bulk material through the treatment bath. Utilizingthe forces of gravity, this vibrator conveyor transports the bulkmaterial in a spiral conveying trough in ascending direction around acolumn type central pipe connected with the conveying trough. Theconveyor together with the support column is lodged in a gasproof vesselcontaining an electrolyte into which the central pipe with the conveyingtrough dips partially. As drive means serve for example oblique-actionvibrators or obliquely set rods. By such drives oscillations are causedin such a way that the bulk material is transported periodically withthe oscillation, gaining height in transport direction through theeelectrolyte. Such vibrator conveyors require relatively little driveforce and permit gentle conveyance of the bulk material. Intensivemovement and good electrolyte exchange as well as uniform currentconsumption over the entire effective surface of the spread-out bulkmaterial are obtained. The conveying trough of the vibrator conveyor canbe made to oscillate via the central pipe, which is connected with theoscillation drive. The central pipe then fulfills, in addition to thetransmission of oscillation, also the task of a supporting structure forthe conveying trough. The trough, leading spirally upward around thecentral pipe, is secured in an especially simple and space-saving manneron the centered central pipe. The oscillation excitation then occurs atlittle cost through an oscillation drive which is disposed above orbelow the central pipe. Current supply to the cathode occurs inside thecentral pipe, while the current to the anode is supplied through thevessel wall U.S. Pat. No. 4,670,120.

SUMMARY OF THE INVENTION

It is now the object of the invention to state an especially simple formof realization of a current supply to one of the electrodes, preferablythe cathode.

According to the invention this problem is solved with thecharacterizing features of claim 1. These supporting stringpieces format the same time a mechanical retention for the conveying trough and anelectric power lead to the bulk material constituting the cathode. Thecontact screws inserted into the stringpiece form a mechanicalconnection between the stringpieces and the conveying trough 2 as wellas a current transmission to the bulk material connected as cathode oras cathode.

BRIEF DESCRIPTION OF THE DRAWINGS

For further elucidation of the invention reference is made to thedrawing, in FIG. 1 of which a device for electrolytic surface coating ofbulk material is illustrated schematically as a section. FIGS. 2 and 3show a form of realization of a supporting stringpiece according to theinvention, which serves at the same time as power lead.

DETAILED DESCRIPTION OF THE INVENTION

A device for electrolytic surface treatment of metallic bulk material,for example for the electrodeposition of aluminum from aproticaluminum-organic electrolytes free of oxygen and water, according toFIG. 1, comprises a central pipe 2 with a bottom 3 and a cover 4 as wellas a hollow-cylindrical sidewall 5. The central pipe 2 protrudes from avessel 6, the cover 7 of which is connected gasproof with the centralpipe 2 via a sealing bellows. A gas cushion 10 is enclosed in the mannerof a diving bell by the bottom 3 of the central pipe 2 and by ahollow-cylindrical extension not specifically indicated in the figure.The central pipe 2 dips partially into an electrolyte 12, the upperlevel of which, marked 13, is indicated dashed in the figure, Theelectrolyte 12 may be for example an aprotic aluminum-organicelectrolyte free of oxygen and water. Above the cover 4 of the centralpipe 2 and hence outside of the central pipe 2 and also outside of thevessel 6 an oscillating drive 16 is arranged, only symbolized in thefigure, which is secured on a bearing block 17 and is relatively freelyaccessible. This oscillating drive 16 brings about in conjunction with amechanism not shown in the figure an oscillating movement of the centralpipe 2 and hence of a conveying trough 18, which is arranged spirallyaround the central pipe 2. The conveying trough 18 contains a bulkmaterial 20 intended to be coated, which is transported inside theconveying trough 18 in the electrolyte 12 and is electrically contactedduring the transport. The conveying trough 18 is secured on supportingstringpieces, which serve at the same time as mechanical retention forthe conveying trough 18 and as power lead to the bulk material 20 andwhich are marked 22 to 29 in the figure. The superposed supportingstringpieces 22 to 25 and 26 to 29, respectively, areelectroconductively connected to an electrode terminal 34, 35 via atleast one bus bar 32, 33 respectively.

Associated with the conveying trough 18 with the inserted contactscrews, intended to be connected as cathode in this form of realization,are anodes, of which only three are shown in the figure forsimplification, marked 37 to 39. Anode 37 is fastened on the vessel wall6, and the anodes 38 and 39 are fastened on the cover of an anode shaft.

A feed shaft, merely indicated in the figure, is marked 41, and adischarge shaft, 42. After one or more circulations inside theelectrolyte 12, the bulk material 20 can be returned to the beginning ofthe conveying trough 18 by actuation of a mechanical switch, which isrepresented in the figure merely as a flap 44 for simplification, andwhich can be operated from the outside by a drive 45.

In the form of realization per FIG. 2, a supporting stringpiece iselectroconductively connected, e.g. screwed, to the bus bar 32 via thecontact shaft 52, and is stably supported in a welded-on coupling in thesidewall 5 of the central pipe 2. For current conduction and at the sametime for mechanical strength serves a contact shaft 52 of electricallyconductive material with a preferably profiled surface, made for exampleof metal, in particular high-strength steel. The profile of the contactshaft 52 is not shown in the figure for simplification. The contactshaft 52 is provided with an electric insulation 54, which may consistfor example of plastic and in connection with a profiled surfacepreferably of a laminated cloth wrap HGW. The resin-impregnated fabricis wrapped in known manner around the contact shaft, thereafter pressedand then hardened.

Passing through the bottom 19 of the conveying trough 18 and theinsulation 54 are several contact screws which serve to attach theconveying trough 18 on the contact shaft 52 and at the same timeestablish an electric connection between the contact shaft 52 and thebulk material 20. At a width of the conveying trough 20 of for example B=300 mm, for example six contact screws for the supporting stringpiecemay be provided, of which only three are shown in the figure forsimplification, marked 56 to 58. For proper current distribution to thebulk material 20 these contact screws 56 to 58 may preferably haveenlarged heads inserted in the conveying trough. These screws aregenerally provided with a safety element not shown in the figure, sothat they will not loosen due to the vibration of the conveying trough18. The contact shaft 52 with its insulation 54 and a seal ring 64 isinserted in a coupling 62, which is made of metal, e.g. steel, and isundetachably connected with the sidewall 5 of the central pipe, forexample by welding. This coupling 62 is provided with a coating 61,which may preferably consist of a self-hardening plastic, in particularphenolic resin, and which covers also the sidewall 5 of the centralpipe. Serving for electric insulation of the contact shaft 52 againstthe central pipe 2 and as abutment is a bushing 66 made of mechanicallystrong, electrically insulating material, preferably glassfiber-reinforced plastic GFK. By means of a first nut not specificallymarked the supporting stringpiece is screwed to the sidewall 5 via thecontact shaft 52. Subsequently, with the second nut, also not marked,the stringpiece is connected to the bus bar 32. Between the shim 68 andthe nut 72 preferably a cup spring 74 may further be provided. In thisform of realization, on the one hand the conveying trough 18 is fixed inthe sidewall 5 of the central pipe 2 and, on the other hand, theelectric contact between the bus bar 32 and the bulk material 20 isestablished.

In a special form of realization of the supporting stringpieces 22 to29, a seal ring 76 may also be disposed closer to the electrolyte 12, inparticular on the end face of coupling 62 toward the electrolyte 12, asillustrated in FIG. 3. For this purpose the insulation 54 is providedwith an annular shoulder 78, which serves as abutment. In this form ofrealization the electrolyte 12 can no longer penetrate into the annulargap between the insulation 54 and the inside wall of coupling 62. Inthis case the inner seal ring 64 is unnecessary.

What is claimed is:
 1. A device for electrolytic surface treatment ofbulk material, comprising: a vibrator conveyor having a conveyingtrough; a central pipe; supporting stringpieces, for mechanicallyattaching the conveying trough on the central pipe and for transmittingcurrent to a cathode, said supporting stringpieces forming anelectrically conducting contact shaft which is electrically insulatedfrom the central pipe and from electrolyte; and contact bolts forattaching the conveying trough to the supporting stringpieces and fortransmitting current from the contact shaft to the bulk material.
 2. Thedevice according to claim 1 wherein the contact shaft has a profiledsurface and a wrapped covering of a laminated cloth HGW.
 3. The deviceaccording to claim 2 wherein insulation material for the contact shaftis surrounded at one end by a coupling, said coupling being undetachablyconnected with the central pipe and being associated with a bushing ofelectrically insulating material as an abutment, with a seal beingdisposed between the bushing and the insulation material.
 4. The deviceaccording to claim 3 wherein the coupling has an inner shoulder at anend thereof toward the bushing, and wherein a seal ring is disposedbetween the inner shoulder and an end face of the insulation material.5. The device according to claim 3 wherein the insulation material hasan annular shoulder, and wherein a seal ring is disposed between theannular shoulder and an end of the coupling toward the electrolyte.